Due to the rising cost of liquid fuel (e.g. diesel fuel) and ever increasing restrictions on exhaust emissions, engine manufacturers have developed dual-fuel engines. An exemplary dual-fuel engine provides injections of a low-cost gaseous fuel (e.g. natural gas) through air intake ports of the engine's cylinders. The gaseous fuel is introduced with clean air that enters through the intake ports and is ignited by liquid fuel that is injected during each combustion cycle. Because a lower-cost fuel is used together with liquid fuel, cost efficiency may be improved. In addition, the combustion of the gaseous and liquid fuel mixture may result in a reduction of harmful emissions.
An example of this type of arrangement is disclosed in U.S. Pat. No. 4,527,516 to Foster. In particular, the '516 patent discloses a dual-fuel engine that includes an inlet pipe connected at one end to a gas source and at an opposite end to the side of an engine cylinder via an inlet port. The pipe is held in the inlet port by a port seal, such that an upper edge of the pipe is spaced below an upper edge of the inlet port. The '516 patent also optionally includes an electronically controlled gas admission valve to control the timing of the gas entry into the cylinder via the inlet pipe.
Although perhaps adequate for some applications, the '516 fuel system may be less than optimal. In particular, the gas inlet pipe and port seal connection may allow the gas to be injected in only a single direction across the cylinder because the pipe is held in place by the seal. This arrangement could result in sub-optimal gas dispersal and less than ideal mixing of the gaseous fuel and diesel fuel because the gaseous fuel can only be directed horizontally across a bottom of the fuel space. Also, the location of the inlet pipe of the '516 system may reduce an amount of time that the inlet pipe is able to actually inject the gaseous fuel, regardless of input from the control valve.
The disclosed dual-fuel system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.